The micro-fibres were analysed before and after testing using a
Scanning Electron Microscope (SEM) to exactly measure diameters,
highlight surface features (which could be correlated to the friction
behaviour) and observe fractured fibres after tensile tests to infer
damage mechanisms. Some examples of the acquired images are
shown in Fig. 2, also highlighting micro-fibre fragilization due to
the damage during sliding in the knotted configuration. For
example, in the case of Kevlar® fibres, degradation was observed
during sliding before fracture (Fig. 2a and b), while little or no
damage was observed in Zylon® fibres, with a clean fibre fracture
away from the knot (Fig. 2d).